1. Field of the Invention
This invention relates to information storage and processing and, particularly, is concerned with methods of erasing information.
2. Description of the Prior Art
Known in the art is a method of erasing information in optical storage devices, wherein portions of an optical information carrier, on which information had been recorded, are exposed to a light beam so that they are reversibly converted into a state having initial optical properties. Such exposure of the optical carrier leads to changes in the degree of crystallization of the recording layer of the carrier, (FR, B, 2, 482 756).
This method is deficient in that it is too lengthy since the optical carrier has to be heated very slowly and the temperature has to be controlled precisely after heating. The method is not efficient and the reliability of repeated recordings is too low because recording and erasing cycles adversely affect the structure of the recording layer, its thickness becomes irregular.
Also known in the art is a method for erasing information recorded on an optical carrier having a recording layer, (U.S. Pat. No. 4 403 318) wherein the optical carrier is subjected to external exposure erasing recorded information, e.g. by heating. To this end, two or more light beams are produced, focused on the carrier, and scanned along the recording layer of the information carrier so that portions of this recording layer are heated differently. This is achieved by changing the density of the beam by changing the density of the beam by changing the radiation intensity or the size of the spot.
This method is deficient in that it cannot provide multiple use of the optical information carrier due to the reasons listed above.